1. Field of the Invention
The present invention relates to a composite fiber and a method for making the same, and a substrate having the composite fiber and a method for making the same, and more particularly to a composite fiber having elastomer and a method for making the same, and a substrate having the composite fiber and a method for making the same.
2. Description of the Related Art
Artificial leather is generally fabricated with the following method. A non-woven fabric (containing fibers made of non-elastomeric polymer such as nylon or polyester) is doped/impregnated in an elastopolymer solution or a latex solution (mainly containing polyurethane (PU)), and the elastopolymer is then cured through a wet or dry process. The non-woven fabric doped with the elastopolymer is cured into a sponge or a block-shaped structure, in which the cured elastopolymer covers and surrounds fiber bundles.
Natural leather has a substrate constructed with a delicate upper layer and a rough lower layer. However, strict control technology is required in the PU-impregnation stage of the artificial leather, and although the PU-impregnated substrate has excellent texture and durability, the fibers are filled with a resin to form a solid construction, resulting in poor air permeability and difficulty in achieving lightweight performance. Moreover, as a solvent is used in PU-impregnation, the fabrication is complicated, and environmental problems may occur.
Most artificial leather using superfine fiber which needs to undergo fiber distribution by using a solvent or lye. Since the fiber distribution process must be implemented with the solvent or lye, severe pollution to the environment will occur.
Japanese Patent Publication No. H04-185777 discloses a method of fabricating artificial leather by using a high-density non-woven fabric substrate to impregnate with low dry content binder resin before PU-impregnation. However, as the distribution of the impregnated binder from the interior to the exterior of the non-woven fabric can hardly be uniform, the fabricated artificial leather lacks softness on the surface, has low inter-layer strength, and cannot be used as a material for shoes in rigorous conditions.
Japanese Patent Publication No. S54-59499 discloses a method of impregnating a wound non-woven fabric substrate made of fine fiber bundles in an aqueous emulsion of a binder resin, and then blowing hot air on only one side of the substrate, so that the binder resin mainly migrates on the side blown with the hot air, and the migration of the resin on the other side of the substrate is suppressed. However, when the migration is prevented according to this method, as a minute amount of aqueous emulsion of the binder resin is left on the other side, the curing degree varies on the two sides of the substrate, and thus it is difficult to fabricate an artificial leather substrate made of fine fibers with no binder resin adhered to the surface thereof.
Taiwan (ROC) Patent Publication No. 200745408 discloses a method of using a fibrous binder to achieve uniform distribution of the binder. In this method, a water-soluble thermoplastic polyvinyl alcohol (PVA) resin is used as a sea composition polymer of sea-island cross-section fibers, and after a non-woven fabric is made, the PVA resin is uniformly distributed in the non-woven fabric through water-solubility and thermoplasticity of the resin. However, as the PVA resin is inelastic and easily solved in water, the whole fabric lacks softness, and is easily attenuated in physical properties and cannot be used any more in a damp environment.
Taiwan (ROC) Patent No. 134197 discloses a method in which a substrate is formed by a matrix fiber and a binder fiber provided with an elastopolymer on its surface. This method is characterized in that the binder fiber is dispersed in the matrix fiber and softened in a fiber assembly of the matrix fiber. The binder fiber used herein is mainly of a core-sheath configuration. During the formation of a fiber substrate, in order to prevent premature adhesion of the fibers, which would affect the quality of the substrate, a mold releasing agent is applied to a part of the surface of the matrix fiber. In this case, although the impregnation with an elastopolymer solution is not needed, the fabrication time and cost are not effectively reduced due to the additional mold releasing agent process.
Therefore, it is necessary to provide a composite fiber having elastomer and a method for making the same, and a substrate having the composite fiber and a method for making the same to solve the above problems.